I read that air and water are transparent to visible light. Animals have adapted so their eyes see these wavelengths. My question is, how surprising is it that both air and water are transparent to the same frequencies? Is that just cosmic chance? (So that sighted animals can see underwater and above it? And species didn't evolve to specialize in exclusively underwater or terrestrial habitats?)

Yes Jackbean,I was referring to the fact that water and air are both transparent in the same spectrum, mostly, so that species don't have to have (tremendously) different vision strategies for use above or below water. Generally, any animal that can see above water can see below it, because water and air are transparent to the same wavelengths.If water and air were transparent in different frequencies, organisms' vision would need to be specialized for use in water, or specialized for use in air. Something that could see underwater would not be able to see the light to which air was transparent.

But there are quite a lot of problems to see underwater, try it, your eyes do not like it. The refraction indices are different and that is sometimes a problem. Besides the transparency of water to light is quite limited, and different at some wavelength. So no cosmic conspiracy here.

Patrick

Science has proof without any certainty. Creationists have certainty without
any proof. (Ashley Montague)

Seals and dolphins, cormorants and iguanas, etc. I'm not arguing with you. I mean to point out that i know of no reason two solutions as different as water and air should be transparent in the same spectrum. It's a heck of a coincidence. It allows for eye physiology such as rods and cones, to be equally useful in two environments, without needing distinct apparatus, one for vision in water, one for vision while in air.